Thanks for this thorough investigation Chris.

On Sep 21, 2016 6:18 AM, "Christopher Gray" <cg...@graytechsoftware.com>
wrote:

> I finally had a chance to figure out the discrepancy between radio power
> readings in the 2.4 GHz band. I've often heard about people getting
> significantly reduced signal when switching from airMAX to ePMP on 2.4
> GHz.. but other people see no difference. In my case, I found a drop of
> about 7 dB going from airMAX to ePMP on a particular PTP link with matched
> settings running 5 MHz channels, but an increase in throughput (which
> really made me want to figure out what was going on).
>
> Following some early morning testing, it turns out: ePMP is reporting
> received power while airMAX is actually reporting receive spectral density
> with units dBm/20MHz.
>
> As a result, if you swap radios from airMAX to ePMP when running 20 MHz
> channels, you should little to no change at all. If you are running 10 MHz
> channels, however, you should expect about 3 dB reduction in reported
> signal, and if running 5 MHz channels, you should see about 6 dB reduction
> in reported signal. [If you are running 40 MHz channels, you should see an
> increase of about 3 dB, but please don't run 40 MHz channels in 2.4 GHz.]
> These reductions are not the result of weaker performance, but simply
> different units in the signal bar.
>
> On a side note relative to poor ePMP performance... ePMP has had a
> firmware issue with calculating output power in FCC areas resulting in
> lower than allowed power output. I've been questioning them about this, and
> they tell me the correct output power calculations should be in the "next
> firmware". Once this is fixed, weaker customers should have a better chance
> of linking up.
>
> [Also, I should note the AF-2X radios also report received power like the
> ePMP.]
>
> -Chris
>

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